elook.org/nutrition
This website details the nutritional information for about 6,000 foods.
http://www.ars.usda.gov/Services/docs.htm?docid=13746
contains data files detailing nutitional content

Students will record what they eat for a given period of time and then use the above website to detail the grams of fat, protein, and carbohydrates for each food. Students will use a pre-existing spreadsheet to enter the data. The spread sheet will be set up to calculate the total calorie content for each food item as well as the total calorie content of all food items using each student's individual data set.

Hi Emily,

This topic will spark the interest of students as it is "real life."
You have a good idea of using a "ready" spreadsheet if it is their first foray into Excel. And, I'm sure their science teacher will be grateful for this introduction to excel that you are giving them.

You may already be planning this, but they could also create bar or pie graphs from their data.

Hope it goes well! Johanna